A “spectacular” ring made by the earliest sapphire craftsmen in Britain for a mystery King has been bought by Yorkshire Museum for £35,000.

The gold ring, declared as treasure after being found by a metal detectorist in 2009 and described as holding national importance, is made of gold, prestige glass and a central sapphire – materials which museum archaeology curator Natalie McCaul admitted would make it “incredibly difficult” to date.

“What is most intriguing for us is that nothing like this has ever been found before in this country,” she said.

“There is no doubt that it was made by one of the finest craftsmen in the land for someone of great wealth and very high standing, but as it is so unique we are still unsure about when exactly it was made.

“This is a spectacular find – a very bold and beautiful ring with a huge sapphire in the centre.

“We are now planning for experts to come and look at the ring in the next few months to help us reveal some of its secrets.”

The ring was found by enthusiast Michael Greenhorn, of the York and District Metal Detecting Club.

The use of sapphire and gold beading suggests it is from the Viking period, but the combination of gold, red and blue glass typically dates from the Anglian style of 700 to 900AD.

Blue glass beads have been found before in York, fuelling belief that the city was a hive of highly-skilled jewellers which welcomed powerful royal visitors.